METHOD OF INCREASING THE WORKING FACTOR (COS. φ) AND THE STABILITY OF ELECTRIC FURNACES.



K. BIRKBLAND. METHOD OF INCREASING THE WORKING FACTGR c0s.q AND THE STABILITY OF ELECTRIC! FURNACES.

1,01 1,01 APPLICATION FILED APB.16,1Q10. Patented Dec 5, 1911.

712572 644 Ea axe/150i W W /zalwwd UNITED STATES PATENT OFFICE.

KRISTIAH BIBKELAND, OF CHBIBTIANIA, NORWAY, ABSIGNOB TO NOBSK HYDRO ELEKTBI8K KVAELS'IOFAKTIESELSKAB, OF CHBISTIANIA, NORWAY.

METHOD or mcnnas'md THE wonxnro moron. (cos. .p) AND THE sTABILITY or ELECTRIC summons.

Specification of Letters Patent.

Patented Dec. 5, 1911.

To all whom it may concern:

Be it known that I, KRISTIAN BIRKELAND, a subject of the King of Norway, residing at Christiania, Norway, have invented certain new and useful Improvements in the Method of Increasin the Working Factor (cos. c) and the Sta ilit of Electric Furnaces; and I do hereby eclare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to a method of increasing the working factor (cos. ip) and the stability of electric furnaces.

Many attempts have hitherto been mad to increase the power factorthe ratio between the amount of work and the product of current and tension of current in electric furnaces working with induction or choking coil inserted in series with the furnace. These attempts, however, have not always turned out satisfactorily.

A simple method to increase the working factor consists in arranging the points of the electrodes farther apart. Thereby the watt component of the alternating current will be increased relatively to the wattless component thus also correspondingly increasing the power factor. At the same time, however, the tendency of the arc to 0 out will be increased andaccordingly the Inertia (stability) of the furnace becomes less.

The present invention has for its object a very simple and very effective means of increasin the power factor and the inertia.

It consists in inserting in series with the furnace instead of one single induction coil, two or more induction coils connected in parallel which may be made either alike or be differently made. Said induction coils are given such dimensions that together they will not let through more current to the furnace than did the single coil.

On account of the small diflerences which the several coils have to one another, even. if they are made practically perfectly simi lar to one another the effect-of the dilfer ences of self induction of the coils, is that the current in each coil does not pass er:- actly simultaneously through the zerohint of theresultant current curve; shoul" the furnace for a moment be on the point of being extinguished, the complete interruption of the current-cannot easily occur for that reason and the points of the electrodes can be set farther a art without the inertia becoming too low, e working factor being at the same time increased.

. The drawing is a diagrammatic representation of an electric furnace embodying my invention, wherein A designates the generator, B, B the electrodes forming the terminals of an electric circuit a. Between one of the terminals and the generator are included two induction coils C, C, which are connected together in parallel, and both are in series in said circuit.

It is quite clear that the resulting current will have zero points, and that the arc may be liable to become extinguished at these points. The danger may, however, be more or less dominating according to the nature of the apparatus used. It is clear, that the danger 1s less, the more rapid the current curve rises from the zero point, that is to say, the greater the time constant is; (L being the coefiicient of self induction and W the resistance of the circuit) and in fact this constant is greater for several induction coils connected in parallel. It should also be remarked that in an arc of the na ture in question there will always exist oscillations (Hertzian waves) of high period; such oscillations are mainly created in those parts of the coils nearest the arc. By using two coils instead of one, it is therefore clear that these oscillations are increased, because the places of origin of them are increased.

I claim:

1. The method of increasing the power factor (cos." c) and the inertia of electric furnaces, which comprises dividing the current from an alternating source into a lurality of parts in parallel and out of ase and supplying the resulting current 0 said parts to one of the electrodes.

2. The method of increasing the ower factor (cos. c) and the inertia of e ectric furnaces, which comprises dividing the current into a plurality of parts out of base and suppllyin the resultant current 0 said partsto t e e ectrodes.

: 3. An electric circuit having two electrodes, a. generator for alternating current, as my invention, I have signed my name in and a plurality of induction coils in the cirpresence of two subscrib' witnesses. cuit between the enerator and one of the KRISTIAN BIRKELAND. electrodes, said in uction coils connected in Witnesses:

5 parallel, and in series in the circuit. HENRY BORDEWICH,

In testimony that I claim the foregoing NANA PEDEBSON. 

